Generally, a liquid infusion apparatus which is used to infuse a medical liquid to a target such as a patient includes a main body, a door, a flexible liquid infusion tube, and a wiggling liquid infusion pump. FIG. 1 is a sectional view illustrating a portion of the typical liquid infusion apparatus. As shown in FIG. 1, the door 2 is openably provided on the main body 1. The liquid infusion tube 3 is disposed such that when the door 2 is closed, it is interposed between the main body 1 and the door 2. The liquid infusion pump includes fingers 4 which are arranged in parallel to each other, and a finger drive means (not shown) which move fingers 4 in a wiggling manner. When the door 2 that is openably provided on the main body 1 is in the closed state, the liquid infusion pump faces the door 2 so that the fingers 4 can compress a portion of the liquid infusion tube 3 interposed between the main body 1 and the door 2. Furthermore, a compressing member 5 is provided on the door 2 such that when the door 2 is closed, the compressing member 5 compresses a portion of the liquid infusion tube 3 interposed between it and the fingers 4. A plurality of coil springs 6 are provided between the compressing member 5 and the door 2 so that the compressing member 5 can elastically compress the liquid infusion tube 3. Although it is not shown in the drawings, a medical liquid injection unit such as an injection needle or catheter is connected to an end of the liquid infusion tube 3.
After the door 2 is closed and the liquid infusion tube 3 is interposed between the main body 1 and the door 2, the finger drive means is operated. Then, the fingers 4 repeatedly successively compress the portion of the liquid infusion tube 3 in the longitudinal direction. The compressing member 5 supports the liquid infusion tube 3 at a position opposing to the fingers 4 that are moving in the above-mentioned manner. Thus, medical liquid supplied from a medical liquid storage means to the liquid infusion tube 3 is transferred in constant amounts along the liquid infusion tube 3 by the compressing operation of the fingers 4 and the supporting function of the door 2. The medical liquid is infused into the target by the medical liquid injection unit. During this process, if an excessive load is applied to the liquid infusion tube 3 by the fingers 4, the compressing member 5 moves away from the liquid infusion tube 3 and supports the liquid infusion tube 3, thus preventing the liquid infusion tube 3 from being damaged.
However, in the conventional liquid infusion apparatus, the compressing member 5 and the coil spring 6 which are used to elastically compress the liquid infusion tube 3 are installed on the door 2. The structure of the door 2 is therefore complex. Further, when the door 2 opens, the complex structure of the door 2 is exposed to the outside, increasing the possibility of the door 2 being damaged. Hence, there is a disadvantage in that a separate element is required to cover the complex structure of the door 2 and protect it. Also the thickness of the door 2 is increased, making it difficult to modify the design of it to compactify the apparatus.
Moreover, if the door 2 opens when the conventional liquid infusion apparatus is being operated, transferring medical liquid from the liquid infusion pump cannot be controlled. In this case, medical liquid supplied from the medical liquid storage means to the liquid infusion tube 3 is directly infused into the target. Depending on the kind of medical liquid, the patient that is the target may be put into a coma or die of shock. Therefore, improvements are required to overcome the above problems.
Furthermore, when the conventional liquid infusion apparatus is being operated, if a portion of the liquid infusion tube 3 that is at an outlet-side based on the liquid infusion pump is undesirably bent or the medical liquid injection unit is filled with medical liquid, the liquid infusion tube 3 may be blocked. If the blocked liquid infusion tube 3 is neglected, infusion of medical liquid is interrupted, and the internal pressure of the liquid infusion tube 3 is increased by medical liquid which is continuously supplied by the liquid infusion pump, thus excessively expanding the liquid infusion tube 3 and damaging it. Thus, a device which can reliably detect whether the liquid infusion tube 3 is blocked during the liquid infusion process is required.